Research Methodology

Question 1

What is an Observational study?

Answer 1

A study which does not intervene in any way

Question 2

What is an experimental study?

Answer 2

A study in which the investigator deliberately intervenes

Question 3

What are the two branches of Observational studies?

Answer 3

Cross-sectional or Longitudinal

Question 4

What are the two types of longitudinal studies?

Answer 4

They are both analytic studies:
Cohort (prospective)
Case control (retrospective)

Question 5

What are key features of a cross-sectional study?

Answer 5

• Are descriptive, and provide a snapshot picture of a community at a point in time
• Can measure prevalence of disease
• Measure exposure and effect at the same time
• Generate hypotheses

Question 6

What are the strengths of cross-sectional studies? (4)

Answer 6

• Relatively simple
• Data collected at around the same time
• Little demanded of subjects
• Does not have problems with prolonged
follow-up

Question 7

What are the weaknesses of cross-sectional studies? (3)

Answer 7

• Lack time dimension (Association not causation)
• Over-interpretation is a considerable danger
• Need a reasonable prevalence so not efficient for very rare conditions

Question 8

What are the key features of case control studies? (3)

Answer 8

• are retrospective (information obtained from past records)
  • Investigate causes of disease
  • Look backwards to past events see whether causes can be identified

Question 9

What are the strengths of case control studies? (2)

Answer 9

• Highly efficient in terms number of subjects required
• Advantages in time study takes and lower costs

Question 10

What are the weaknesses of case control studies? (4)

Answer 10

• The Advantage that the outcome has already happened is also the great disadvantage
• All information on factors has to be collected after event has occurred (retrospective)
• Information is likely to be incomplete or inaccurate, as major causal events many have happened many years ago.
• Bias in the recall of events, as case subjects tend to give different responses to the control subjects

Question 11

What is Bias?

Answer 11

Inaccuracy that is different in its size or direction in one of the groups under study

Question 12

Give 6 sources of bias

Answer 12

• Selection
• Allocation
• Measurement
• Recall
• Observer
• Publication

Question 13

What are the key features of cohort studies? (4)

Answer 13

• Are prospective (data collected forward from a given starting point)
  • Group individuals identified and watched to see how progress
  • Essential element time flows forward
• The time relationship between exposure and outcome is appropriate so can measure incidence rate of outcomes

Question 14

What are the strengths of cohort studies? (4)

Answer 14

• Multiple end-points can be assessed
• Cause to effect time sequence clear
• All measures of risk can be assessed
• Exposure prior to outcome avoiding bias

Question 15

What are the weaknesses of cohort studies? (3)

Answer 15

• Time if the outcome does not occur for a long time after exposure
• If outcome not frequent then must involve large number subjects to observe events
• Confounding

Question 16

What is confounding?

Answer 16

Confounding is distortion of the exposure -outcome association, Brought about by the association of another factor with both outcome and exposure

Question 17

What are the key features of randomised controlled trails (RCTs)? (4)

Answer 17

• Gold standard
• Can test causal hypothesis that change in intervention produces change in the outcome
• Designed so subjects receiving intervention are same as those in a control group
• Best achieved by randomization

Question 18

What are the strengths of RCTs? (2)

Answer 18

• Randomization will control for confounding
• Double blinding will control for bias

Question 19

What are the weaknesses of RCTs? (3)

Answer 19

• Requirements in terms of organization, time, cost resources and ethical questions raised
• Assessment of small improvements in treatment may need large numbers
• Time may be problem where long follow up needed e.g. drug prolongs life by preventing death from a specific cancer - Treatment may be obsolete by the time results available

Question 20

Explain the meaning of the term ‘hierarchy of research study design’

Answer 20

EBD hierarchies rank study types based on the rigour (strength and precision) of their research methods from strongest (top of pyramid) to weakest (bottom of pyramid).

Question 21

What are clinical trials?

Answer 21

• Concerned with effectiveness
• Often related to drug therapy but also other interventions e.g. surgery, physical exercise, diet, advice regarding prevention
• Also concerned with side effects